Crystal and method of producing the same



May 2, 1933. B. KJELLGREN CRYSTAL AND METHOD OF PRODUCING THE SAME Filed April 27, 1929' INVENTOR l gin 6T flue; L fiE/V /4 $15.10, gaudy:

ATTORNEYS Patented May 2, 1933 BENGT KJELLGBEN, OF CLEVELAND, OHIO, ASSIGNOR TO THE BRUSH DEVELOPMENT COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO CRYSTAL AND METHOD OF PRODUCING THE SAME Application filed April 27, 1929. Serial K0 3583329.

This invention relates to crystals and the method of producing the same, particularly to crystals of clear, uniform structure for use in the manufacture of piezo-electr1c apparatus.

One of the objects of this invention is to provide an easy method of producing seeds or neuclei for growing crystals.

Another object of this invention is to provide a method of producing crystals whereby non-homogeneity of the crystal structure 1s materially lessened by the substantial exclusion of the seed from which the crystal is pro duced.

Another object is to provide a method of producing seeds or nuclei of uniform size and characteristics.

A further object is to provide a method of producing a seed wherein a crystal of special proportions may be readily produced from the seed according to the shape and orientation of the same. v

A still further object is to provide a method of producing a clear crystal uniform in structure wherein a seed cut from a crystalline mass in predetermined relationship, is immersed in a solution of a crystal salt.

Another object is to provide a method of producing crystals wherein the seeds used in producing the same are cut from a crystalline mass in predetermined relationship to the crystalline axes thereof.

Still another object is to provide a clear crystal of large and uniform size which does not have mother liquor contained within the same.

These being among the objects of the pres ent invention, the same consists of certain methods and operations, and combinations of parts to be hereinafter described with reference to the accompanying drawing, and then claimed, having the above and other objects in view.

Crystals are used among other things in the'purification of chemicals and to a very great extent in the making of piezo-electric apparatus. It is, therefore, very desirable in these arts that the crystals be large, uni

form, and clear, and that they be practically free of the mother liquor which is quite frequently contained within the same. Furthermore, it is very desirable for most purposes that the crystal structure be substantially free of the seed from which it is produced.

Heretofore, seed crystals have usually been produced by increasing the saturation of the crystal salt solution, as by gradually reducing the temperature of the salt solution until a plurality of small crystals of various shapes and sizes are formed and deposited on the bottom of the vessel containing the salt solution. The most perfect of these small crystals are selected, washed and dried and are used as seeds for growing larger crystals.

The number of perfect usable seeds is, however, usually a very small portion of the total number of seeds deposited. The selected seed crystals are either placed on the bottom of a vessel containing a crystal salt solution, or are suspended in the solution by a string or small wire, and the saturation of the solution is then increased by lowering the temperature of the same, by introducing more salt into the solution or by any other suitable method. As soon as the solution tends to become-supersaturated the seed crystals begin to increase in size and large crystals are gradually formed. The crystal seed in crystals formed in this manner remains embedded in the crystal structure plainly discernible in the center or bottom face of the same.

Crystals grown by this prior method are non-homogeneous in structure due to the inclusion of the seed in the bottom surface or central portion thereof, and tend to grow to proportions which cannot be controlled, since they are peculiar to the habits of the salt being crystallized.

The present invention proposes an improved method wherein superior crystals having predetermined proportions not necessarily characteristic of the salt to be crystallized, may be readily produced from seeds cut to predetermined shape from a crystalline mass of the salt to be crystallized or from a salt of similar crystalline habits.

In the drawing, crystals of Rochelle salt are shown for the purpose of illustration and explanation, but it is to be understood that about to be described, vis:equally adaptable for producing crystals-of other-salts. I I 1 I I i I In the drawing, Figure Ilis a1fragmentaryI perspective view of a- Rochelle salt. crystal showin in broken outline I angular =seecl' shownwinzbroken outline'in "Fig; '1 cut parallel- .co the. major longitudi n I f Fig. 4 is a perspective- View: of the short. I rectangular seed shown iii-broken. outline in: f

":lFi 1'Icuftparallel to.thevmajorlongitudi j nafaxi'g' I I I I tallize on the exposed surface of the: seed.- ltis obvious'that it may be planted torest snumlyin thedepression or partly in: :the I seed shownin brokenfoutlinle in Fig. 1 cut. parallel to I the majortransverse a'xis. i I I I gi ig-B'iSa U, and narrow: seedsj'shown in broken outline in Fig. 1' cut parallel: to the major. longitudinal s aI p lur lit fg seeds' to:heicuttherefrom 5 I Fig. 2 is a perspective 1 view of the short:

"Fig.3 is a perspective view of the triperspective; view of ft-he long Fig. 6 is a perspective view of a crystal:

; produced from the seed. shown in: Fig. 5, a: I

I portion of? the: crystal being-broken, away to; E showithe-seed. 1 I I II i :F.g

produced from the seed shown: in Fig. :4, a I portionof the crystal being; broken swayed 'sh wth i' i n? i f I Fig; 8 1s a perspective view of a crystal produced from? a seed. which produced from the seed shown in; Fig; 2, a portion of the crystal being broken away 1 7- is a pers eduve view; at :crystal ispilantedin an i upright position. I I I I 1 f 5 I Fig. 9 is a perspectlve view of a icrysmr to show the seed.

Fig. 10 is a section through one form of apparatus used in producing crystals showin a partly formed crystal in cross section.

aeferring to the accompanying drawing in which like numerals refer to like parts throughout the several. views, and particularl to Fig. 1, a fragmentary portion of a Roc elle salt crystal 10 is shown as having a minor or electrical axis H, a major transverse axis b-b and a major longitudinal axis o0.

For the purpose of explanation it will be assumed that it is desired to produce the half crystal 11 shown in Fig. 6. The crystalline axes just described are first determined, either by inspection or test, for the selected crystal 10 from which the seed is to be taken, and the rectangular seed 13 as shown in Fig. 5 is cut from the crystal 10 parallel to the major longitudinal axis 00 as indicated by the broken outline 13a of the seed in Fig. 1. The most convenient method of cutting the seed from the crystal 10 is to use a modified band saw, although it is to be understood that other practical cutting devices may be used.

Commercially, a crystal having as much available clear homogeneous material as pos- 5 sible is desired and this type of crystal is as the, crystal .11 .exampiei. w II Thefseed 13 desired shape: is ready to be :used for; pro:

depression so that the salt so depression,; and 1 that the f'saltl solution will I after it has: been cut to the: ducing the crystal llan'd-is' preferably placed; I 5 i in a depression l'formed :in thebottom :15- I of I the: vessel 16; E It. is preferable; that: the I z bottom 15 be: formed. ;o f;a cushioning material, such as rubber on other: shock absorbing substance, so that theformationof extreme I I 5 L =ous crystallinecenters dueto mechanical ,g= I shocks or vibrations,is materially reduced. I

" As just: pointed out, the :seed:13 cut from f tionwil ryssg I crystallize on I the; exposed. surfaceof the I I seed regardless of whether: theseedprojects I v v Z 1 I I above the surface of thebottom; of the vessel; 3

isfiush withjthe surface: or; is; even; positioned I I below the surface-. The preferable method of i plantingz the seed,- however, isto formthe I depression 14; to; such a depth that whenthe I 3 seed: is positioned therein the upper face of 1 .the seed: will lie substantially flush withthe 3 surface of the. 5 bottom 15, as; illu st rated in Fig. :10, so. that when the salt; so

lutionyis;-. I crystallized on the exposed surface 015 th I seed, la-the seed will 1101; be included in the 1 g the surfacethereof,- as shown: in Fig. .6, a I

portion of the crystal structure being broken away to show this feature.

However satisfactory results have been obtained by planting the seed with its upper face positioned below the surface of the bottom of the vessel containing the salt solution. This method causes a crystal to be grown similar to the one shown in Fig. 7, wherein the seed is separated from the adjacent crystal face by a thin growth 30 of crystalline material.

Satisfactory results have also been obtained by planting the seed in the depression in such a manner that a portion of the same projects above the surface of the bottom of the vessel. The salt solution crystallizes about the exposed surface of the seed and produces a crystal similar to the one shown in Fig. 9 wherein a small portion of the seed is incorporated in the body thereof at the plane of crystalline growth.

A filtered Rochelle salt solution 17 made alkaline corresponding to about 0.1 normal sodium or potassium hydroxide solution and 1 I crysta i S tur but will lie external to 2 I I I I I I has dropped to about 41 degrees C'., the seeds are planted in the desired manner as previously described, and the top 18 is placed over the vessel 16. The temperature of the solution is then allowed to drop to the saturation point. This temperature is maintained until the conditions in the solution are in equilibrium, that is, until the seeds have stopped growing. When an equilibrium of the solution is reached, a slow reduction of the temperature of the same is begun and the crystal 11 starts to grow about the exposed surfaces of the seed 13. It is very desirable that a circulatory or to-and-fro motion be imparted to the solution during the formation of the crystal 11 as indicated by-the arrows 19. The sides of the depression 14, in the bottom 15 of the vessel 16 exert sufiicient friction against the sides of the seed crystal 13 to hold the same in position during the movement of the solution. As the crystal 11 gradually increases in size the temperature of the soluiton may be gradually lowered until the crystal reaches a suitable size. It may i be desirable in some cases to use an evaporation process or even a combination of heat and evaporation. This, however, is optional.

As the crystal 11 grows on the exposed surface of the seed 13 its crystalline axes are de termined by and correspond to the axes of the seed 13. When the crystal 11 has reached a suflicient size it is removed from the solution with the seed 13 adhering thereto. The entire seed 13, as shown in Fig. 6, lies outside of the surface of the crystal 11, and can be easily removed in any suitable manner, leaving no trace of the seed 13 in the body of the crystal structure. If, however, the crystal has been grown from a seed which was lanted with a portion extending above the bottom of the vessel, a small portion extends into the crystal structure adjacent the plane of crystalline growth, as shown in Fig. 9. The bottom face of the crystal in this case can be cut off to remove the slight trace of the seed. The crystal may then be cut into homogeneous slabs to be used for the purpose for which they are intended.

The ratio of cross section to length in'the produced crystal may be controlled by the relative length and cross section and orientation of the seed crystal. The seed 13 is shown as being relatively long and narrow and consequently the crystal 11 produced from the seed is also long and narrow. If the short crystal 20 shown in Fig. -7 is desired, the short seed crystal 21 shown in Fig. 4 is cut parallel to the longitudinal axis cc of the crystal 10 as indicated by the broken outline 21a in Fig. 1. If the crystal 22 shown in Fig. 9, which is shorter in length than width, is desired a seed 23 shown in Fig. 2' is cut on the broken lines 23a of' the crystal 10 parallel to the transverse axis 5-6. If the full crystal 24 shown in Fig. 8 is desired the seed crystal 13 is planted on one of its ends 1n an upright position, and may be held in place by insertion into ahole formed in the bottom of the vessel, or suspended in the solution by a string.

I Although 't is preferable to plant the seeds 1n depressions in the bottom of the vessel contalnmg the salt solution, as previously described, the advantageous characteristics of the previously described cut seeds may be utilized without planting the seeds in depres- 4 sions, by planting the seeds directly on the flat bottom of the vessel containin the solut1on to. be crystallized. Very satisfactory results have been obtained by planting out seeds in this manner.

In commercial practice it is usually desirable to produce crystals of a single shape most suitable for the purpose for which they are intended. In this case a plurality of slabs are cut from a clear crystal or a portion thereof and the slabs are cut into equal parallel bars of suitable length and sizefor seeds. All crystals produced from these parallel bars or seeds will have the same general characteristics. That is,they will have substantially the same shape or length-width ratio, and under similar growing conditions, the same size and weight.

It 1s apparent that large, homogeneous crystals free from flaws or contaminations can be produced by the method just described. By usmg the method herein described, large clear crystals homogeneous in structure have been produced in three weeks time from seeds having predetermined proportions, which crystals varied in weight according to growmg conditions, from three-quarters to five pounds. It is thus possible to produce a maxunum of perfect usable slabs with minimum waste in cutting, from a single crystal because of the uniform and controlled shape and homogeneity, and also to produce a maximum of uniform crystals in a minimum time.

By the method of the present invention crystals having ratios of length to breadth varying from .5 to 6 have been produced. It is readily seen that the proportions of a crystal can be controlled by the proportions of the seed, and that large seeds of *homo geneous structure can be produced as easily as short seeds, and with considerable more efiiciency and rapidity than by the heretofore used method of growing seeds.

It is further apparent that satisfactory perfect crystals can be readily produced by the present invention which are suitable for use in the arts of making piezo-electric apparatus, optical apparatus, and thelike.

This method may also be used to advantage in the purification of chemicals by the efficient production of large crystals from the mother liquor or other contaminations.

It is to be understood that the shapes of crystals and the p rticular methods and op- 5 erations'set fort are for explanation and illustration only and that formal changes can be made in the invention without departing from the spirit and substance of the broad m- 'vention, the sec e of which is commensurate with the appen ed claims.

4 What I claim is:

1. The method of producing crystals, which consists in cutting a seed cr stal from a crystalline mass in redetermmed relationship to the crystalline axes of said mass,

planting said seed in a depression in the bottom of a vessel containing a solution of the salt to be or stallized so that the salt solution will crystal 'ze on the exposed surface of the seed, and causing said solution to crystallize on said seed.

2. The method of producing a crystal, which consists in planting a seed in a depression in the bottom of a vessel containing a solution of the salt to be crystallized, and causing said solution to crystallize on the exposed surface of said seed.

3. The method of producing crystals, which consists in plantin a seed in a solution of the salt to becrystal ed, protecting the bottom and portions of the sides of the seed from'the solution, and causing the solution to crystallize on the unprotected portion of the seed.

4. The 'method of producing crystals, which consists in cutting a seed crystal om a crystalline mass in redetermined relationship to the crystalline axes of said mass, planting said seed in a vessel containing a solution of the salt to be crystallized, with the greater portion of said seed encased by the bottom of said vessel, and causin said solu tion to crystallize on the expose surface of said seed.

5. The method of producing crystals I which consists in cutting a seed crystal from a crystalline mass in redetermined relationship to the crystalhne axes of said mass, planting said seedin a depression formed in the bottom of the vessel containing a solution of the salt to be crystallized with the greater ortion of the surface of said seed concealed y said depression, and causing said solution to crystallize about the exposed surface of said seed, whereby said seed will lie outside the plane of crystalline growth of the produced crystal.

6. The method of producing crystals,

which consists in cutting a seed crystal from a crystalline mass in predetermined relationship to the crystalline axes of said mass, planting said seed in a solution of the salt to be crystallized with the greater portion of said seed positioned below the plane of the crystal to be produced, and causing said solution to crystallize about the exposed surface of said seed. 7

7 The method of roducing crystals, which consists in concea mg the greater portion of a seed crystal in a cushioning material, and causing a solution of the salt to be crystallized to crystallize on the exposed portion of said seed, whereb the greater rtion of said seed crystal will lie externa y of the produced crystal.

8. The method of producing crystals, which consists in cutting a seed crystal from a crystalline mass in predetermined relationship to the crystalline axes of said mass, concealing the greater portion of said seed crystal in a cushionin material carried by a vessel containing a so ution of the salt to be crystallized, and causin said solution to crystallize about the expose surface of said seed crystal to form a crystal with the greater portion of said seed positioned externally thereof.

9. The method of producing large crystals of the Rochelle salt type which consists in cutting a seed crystal from a crystalline mass in predetermined relationship to the crystalline axes thereof, planting said seed in a salt solution, protecting the greater part of the surface of said-seed from said solution, and causing said solution to crystallize about the exposed surface of said seed so that the said seed will lie outside the produced crystal.

10. The method of producing a large homogeneous crystal of the Rochelle salt type having a weight in excess of three-quarters of a pound, which consists in cutting a seed crystal from a crystalline mass in predetermined relationship to the crystalline axes thereof, planting said seed in a depression in the bottom of 'a vessel containing a solution of the salt to be crystallized with the greater portion of the surface of said seed concealed by the walls of said depression, and causing said solution to crystallize about the exposed surface ofsaid seed whereby said seilad will lie externally of the produced crysta 11. The method of producing crystals long in length and narrow in width, which consists in determining the crystalline axes of a crystalline mass, cutting a seed portion from-said mass parallel to the major longitudinal axis of the mass, planting said seed in a solution of the salt to be crystallized and causing said solution to crystallize on said seed.

12. The method ofproducing crystals of eater width than length, which consists in e'termining the crystalline axes of a crystalline mass, cutting a seed portion from saidmass parallel to the major transverse axis of said mass, planting said seed in a solution of the salt to be crystallized and causing said solution to crystallize on said seed.

13. The method of producing a large crystal of the Rochelle salt type, which consists Ill in determining the crystalline axes of a crystalline mass of Rochelle salt or the like, cutting a seed crystal from said mass'in predetermined relationship to the crystalline axes thereof, planting said seed in a vessel containing a solution of the Rochelle salt type, and causing said solution to crystallize on said seed.

14. The method of producing large crystals and controlling the dimension of the crystal relative to the major transverse or major longitudinal axis of the crystal, which comprises determining the crystalline axes of a crystalline mass, cuttinga seed from said crystalline mass with the longitudinal dimenslon of the seed parallel, to the crystalline axis along which the larger dimension is desired, planting said seed in a vessel containing a solution of the salt to be crystallized, and causing said solution to crystallize on said seed. 7

In testimony whereof I affix my signature.

. BENGT KJELLGREN. 

